I taught myself to knit because my Mom crocheted and there was NO WAY I was going to do that 'old persons' craft.
Heh .. less than 6 months after I taught myself to knit I taught myself to crochet because the idea of knitting an afghan was daunting.
I prefer to crochet, it seems to fit me better and so I've made it a point to learn more than the typical stitches that crocheters use. I've nothing against things like granny squares but I don't do them because I wanted crochet to be more challenging for me. It sounds really stupid when I write it out like this but I needed (at the time) to differentiate the crochet *I* did from the crochet my Mom did.
I've found that no matter whether I'm doing the simple stitches or the more complex that it relaxes me and I feel a sense of accomplishment. The more stressed I am with life the more I crochet. I didn't realize that until I went on a particularly stressful business trip and was feeling out of sorts while there and I headed to the craft store and picked up some thread and a hook and went straight back to the hotel and began working on a project. I felt more calm and began to realize that crochet, for me, was more than just accomplishing a tangible task, it was mental for me too.
I think my favorite thing to do is tunisian though, partially because it has the elegant look of knitting (and similar technique) but it's easy like crochet.
My favorite tunisian site is
Chez Crochet - the creator has a book, The Encyclopedia of Tunisian Crochet which is wonderful and her instructions are very clear.